1. Field of the Invention
This invention relates generally to a high-lift materials handling apparatus and, in particular, to a high-lift materials handling apparatus having an extended reach that may be utilized in low-clearance applications.
2. Description of the Prior Art
In a host of working environments it has become expedient to employ a high-lift materials handling apparatus having an extensible boom which is provided with a materials handling implement on the free end thereof. Such apparatus, otherwise known as a high-lift loader, facilitates the manipulation of articles from a remote location both vertically and horizontally. High-lift loaders have proven useful in a wide variety of materials handling applications in that loads can be picked up, delivered to the required site and lifted to and placed on a desired elevated surface, without the necessity of special or separate handling to transfer the load from the load handling apparatus to the elevated position. This type of apparatus has the further advantage of being able to pick up a load from a remote station which may not be stable enough to support the apparatus and deliver it to another remote station without requiring the apparatus itself be displaced completely to such location.
It will be readily appreciated that in certain applications, especially those involving military operations, it is important to provide a materials handling apparatus that may have its load handling means enter a low-height area, such as a truck or container, and lift and remove various objects therefrom. The materials handling apparatus must also have the ability to transport such objects to a point remote from but in proximity to their required location and place the objects in such location from the remote point, all while maintaining the load in a level orientation.
In conventional extended-reach materials handling apparatuses, the equipment generally includes a telescoping lift arm, commonly referred to as a boom, which is pivotally carried on a self-propelled vehicle. A separately pivotable carriage assembly to which the load handling means is attached is supported on the free end of the boom. Usually, the carriage assembly must be of sufficient height to reach from the boom end to the ground in order to pick up articles as the boom itself is not able to reach to the ground while in its retracted position.
While such apparatus may function reasonably well in certain applications, it is unsuitable for usage in a low access height environment due to the typical height of the carriage assembly. In such an application the tall carriage assembly prevents the entrance of the load handling means into a confined height area, such as a partially loaded truck or container.
One prior art apparatus has attempted to alleviate the above-described shortcoming of other prior art devices. In such apparatus, a separate tilt beam is pivotally affixed to the boom and the load handling means is pivotally attached to the end of the tilt beam thereby eliminating the tall carriage assembly of the previous systems.
A distinct shortcoming of the last-described apparatus relates to the ability of such apparatus to maintain the load level during tilting of the tilt beam relative to the boom. As will be readily appreciated, in such a prior art system when the tilt beam is tilted relative to the boom, the load will also be tilted and, if compensation for such tilting of the load is not provided, the load will be tilted to a position in which it becomes unstable and ultimately is lost. In an attempt to rectify such a situation, the prior art apparatus includes a complicated and costly system of hydraulics and electrical level sensors and controls to correct the fork attitude during tilting of the tilt beam. This system is not adequate to accurately level the load during the operation of the boom.
The subject invention is directed toward an improved extended-reach materials handling apparatus which overcomes, among others, the above-discussed problems and provides apparatus effective in performing extended reach functions in a low-height area without requiring the additional complicated, costly and inefficient electro-hydraulic fork leveling systems of previous apparatuses.